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Planck early results. XVI. The Planck view of nearby

Lahteenmaki, A.; Poutanen, T.; Natoli, P.; Polenta, G.; Bartlett, J.G.; Bucher, M.; Cardoso, J.-F.; Catalano, A.; Delabrouille, J.; Ganga, K. Total number of authors: 250

Published in: Astronomy & Astrophysics

Link to article, DOI: 10.1051/0004-6361/201116454

Publication date: 2011

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Citation (APA): Lahteenmaki, A., Poutanen, T., Natoli, P., Polenta, G., Bartlett, J. G., Bucher, M., Cardoso, J-F., Catalano, A., Delabrouille, J., Ganga, K., Giraud-Heraud, Y., Patanchon, G., Piat, M., Rosset, C., Smoot, G. F., Ashdown, M., Hobson, M., Lasenby, A., Stolyarov, V., ... Gorski, K. M. (2011). Planck early results. XVI. The Planck view of nearby galaxies. Astronomy & Astrophysics, 536, A16. https://doi.org/10.1051/0004-6361/201116454

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A&A 536, A16 (2011) Astronomy DOI: 10.1051/0004-6361/201116454 & c ESO 2011 Astrophysics Planck early results Special feature

Planck early results. XVI. The Planck view of nearby galaxies

Planck Collaboration: P. A. R. Ade71, N. Aghanim47,M.Arnaud58, M. Ashdown56,4, J. Aumont47, C. Baccigalupi69,A.Balbi27, A. J. Banday74,7,63,R.B.Barreiro53, J. G. Bartlett3,54,E.Battaner76, K. Benabed48, A. Benoît46,J.-P.Bernard74,7, M. Bersanelli24,40, R. Bhatia5, J. J. Bock54,8, A. Bonaldi36,J.R.Bond6,J.Borrill62,72,F.R.Bouchet48, M. Bucher3,C.Burigana39, P. Cabella27, J.-F. Cardoso59,3,48, A. Catalano3,57,L.Cayón17, A. Challinor50,56,9,A.Chamballu44, R.-R. Chary45,L.-YChiang49,P.R.Christensen66,28,D.L.Clements44, S. Colombi48, F. Couchot61, A. Coulais57, B. P. Crill54,67, F. Cuttaia39,L.Danese69,R.D.Davies55,R.J.Davis55,P.deBernardis23, G. de Gasperis27,A.deRosa39, G. de Zotti36,69, J. Delabrouille3, J.-M. Delouis48, F.-X. Désert42, C. Dickinson55,H.Dole47,S.Donzelli40,51, O. Doré54,8,U.Dörl63, M. Douspis47, X. Dupac31, G. Efstathiou50,T.A.Enßlin63, F. Finelli39, O. Forni74,7, M. Frailis38, E. Franceschi39, S. Galeotta38, K. Ganga3,45,M.Giard74,7, G. Giardino32, Y. Giraud-Héraud3, J. González-Nuevo69,K.M.Górski54,78,S.Gratton56,50, A. Gregorio25, A. Gruppuso39,F.K.Hansen51,D.Harrison50,56,G.Helou8, S. Henrot-Versillé61, D. Herranz53,S.R.Hildebrandt8,60,52, E. Hivon48, M. Hobson4,W.A.Holmes54,W.Hovest63,R.J.Hoyland52,K.M.Huffenberger77,A.H.Jaffe44,W.C.Jones16,M.Juvela15, E. Keihänen15, R. Keskitalo54,15,T.S.Kisner62, R. Kneissl30,5, L. Knox19, H. Kurki-Suonio15,34, G. Lagache47, A. Lähteenmäki1,34, J.-M. Lamarre57,A.Lasenby4,56,R.J.Laureijs32,C.R.Lawrence54, S. Leach69,R.Leonardi31,32,20, M. Linden-Vørnle11, M. López-Caniego53, P. M. Lubin20, J. F. Macías-Pérez60,C.J.MacTavish56, S. Madden58,B.Maffei55,D.Maino24,40, N. Mandolesi39,R.Mann70,M.Maris38, E. Martínez-González53,S.Masi23,S.Matarrese22, F. Matthai63, P. Mazzotta27, A. Melchiorri23, L. Mendes31, A. Mennella24,38, M.-A. Miville-Deschênes47,6, A. Moneti48,L.Montier74,7, G. Morgante39,D.Mortlock44, D. Munshi71,50, A. Murphy65, P. Naselsky66,28, P. Natoli26,2,39,C.B.Netterfield13, H. U. Nørgaard-Nielsen11, F. Noviello47, D. Novikov44, I. Novikov66, S. Osborne73,F.Pajot47, B. Partridge33, F. Pasian38, G. Patanchon3, M. Peel55, O. Perdereau61,L.Perotto60,F.Perrotta69, F. Piacentini23,M.Piat3, S. Plaszczynski61, E. Pointecouteau74,7, G. Polenta2,37, N. Ponthieu47, T. Poutanen34,15,1, G. Prézeau8,54,S.Prunet48, J.-L. Puget47, W. T. Reach75,R.Rebolo52,29, M. Reinecke63, C. Renault60, S. Ricciardi39, T. Riller63, I. Ristorcelli74,7,G.Rocha54,8,C.Rosset3, M. Rowan-Robinson44, J. A. Rubiño-Martín52,29, B. Rusholme45, M. Sandri39,G.Savini68,D.Scott14,M.D.Seiffert54,8, P. Shellard9,G.F.Smoot18,62,3, J.-L. Starck58,10,F.Stivoli41, V. Stolyarov4, R. Sudiwala71, J.-F. Sygnet48,J.A.Tauber32, L. Terenzi39,L.Toffolatti12,M.Tomasi24,40, J.-P. Torre47, M. Tristram61, J. Tuovinen64,M.Türler43, G. Umana35, L. Valenziano39,J.Varis64,P.Vielva53, F. Villa39, N. Vittorio27,L.A.Wade54,B.D.Wandelt48,21,D.Yvon10, A. Zacchei38, and A. Zonca20 (Affiliations can be found after the references)

Received 7 January 2011 / Accepted 10 June 2011

ABSTRACT

The all-sky coverage of the Planck Early Release Compact Source Catalogue (ERCSC) provides an unsurpassed survey of galaxies at submillimetre (submm) wavelengths, representing a major improvement in the numbers of galaxies detected, as well as the range of far-IR/submm wavelengths over which they have been observed. We here present the first results on the properties of nearby galaxies using these data. We match the ERCSC catalogue to IRAS-detected galaxies in the Imperial IRAS Faint Source Catalogue (IIFSCz), so that we can measure the spectral energy distributions (SEDs) of these objects from 60 to 850 μm. This produces a list of 1717 galaxies with reliable associations between Planck and IRAS, from which we select a subset of 468 for SED studies, namely those with strong detections in the three highest frequency Planck bands and no evidence of cirrus contamination. The SEDs are fitted using parametric dust models to determine the range of dust temperatures and emissivities. We find evidence for colder dust than has previously been found in external galaxies, with T < 20 K. Such cold temperatures are found using both the standard single temperature dust model with variable emissivity β, or a two dust temperature model with β fixed at 2. We also compare our results to studies of distant submm galaxies (SMGs) which have been claimed to contain cooler dust than their local counterparts. We find that including our sample of 468 galaxies significantly reduces the distinction between the two populations. Fits to SEDs of selected objects using more sophisticated templates derived from radiative transfer models confirm the presence of the colder dust found through parametric fitting. We thus conclude that cold (T < 20 K) dust is a significant and largely unexplored component of many nearby galaxies. Key words. galaxies: photometry – submillimeter: galaxies – infrared: galaxies – galaxies: ISM

1. Introduction on the properties of dust and how this relates to other aspects of galaxies and evolution. However, the strong tempera- Dust is an important constituent of the interstellar medium (ISM) ture dependence of the spectral energy distribution (SED) of dust of galaxies. Whilst some properties of dust in our own and very emission, combined with limited wavelength coverage, means nearby galaxies can be studied through its absorption of starlight, that IRAS was relatively insensitive to dust below a temperature it was the IRAS satellite that first allowed dust emission to be of ∼30 K. Observations of dust in our own Galaxy by the FIRAS directly observed in large samples of external galaxies (e.g., instrument on COBE (Reach et al. 1995) found evidence for dust Devereux & Young 1990). The all-sky IRAS survey at 12, 25, at several different temperatures. This included a widespread 60 and 100 μm in wavelength provided much new information component at 16–21 K, and another at 10–14 K associated with molecular clouds in the inner Galaxy. A third widespread colder  Corresponding author: D. L. Clements, e-mail: [email protected] component, at 4–7 K, was later identified with the cosmic

Article published by EDP Sciences A16, page 1 of 16 A&A 536, A16 (2011) infrared background (CIB; Puget et al. 1996; Fixsen et al. 1998). to establish the range of dust temperatures and other properties None of these components would be detectable in external galax- found locally; and thus to set the local baseline against which ies by IRAS. COBE-DIRBE observations also detected 56 ex- higher redshift studies, and especially studies of the SMGs re- ternal galaxies, finding an average dust temperature of 27.6K sponsible for the CIB, can be compared. (Odenwald et al. 1996). The rest of this paper is organised as follows. In Sect. 2 we Observations at longer far-infrared (FIR) or submillimetre give details of Planck’s observations of local galaxies and the (submm) wavelengths from the ground (e.g., Dunne et al. 2000), ERCSC. We also discuss the results of matching ERCSC galax- from space (e.g., Dale et al. 2005) or in combination (e.g., ies to sources observed by IRAS. In Sect. 3 we present a com- Willmer et al. 2009), have provided hints that cooler dust plays parison of the ERCSC with existing data from ground-based ob- a significant role in nearby galaxies. Observations with Herschel servatories. Section 4 presents the results of fitting parametric of pre-selected objects (e.g., Boselli et al. 2010) provide valu- models to the dust SEDs of ERCSC galaxies, while Sect. 5 dis- able data at 250 to 500 μm, which constrain the long wave- cusses the results of physical template fitting. Finally, we draw length dust properties for specific populations. Moderate area conclusions in Sect. 6. Throughout this paper we assume a con- −1 −1 surveys with Herschel (e.g., H-ATLAS Eales et al. 2010a,cov- cordance cosmology, with H0 = 70 km s Mpc , ΩΛ = 0.7and 2 ering up to 550 deg from 100 to 500 μm) provide unbiased stud- ΩM = 0.3. ies of the far-IR/submm population. However, the availability of the Planck1 Early Release Compact Source Catalogue (ERCSC) provides a long wavelength counterpart to IRAS, allowing us an 2. Planck observations of nearby galaxies unbiased view of the FIR-to-submm SEDs of a large sample of nearby (z < 0.25) galaxies. We are now, for the first time, able to 2.1. The Planck mission examine the role of cold dust for a wide range of objects in the local Universe. Planck (Tauber et al. 2010; Planck Collaboration 2011a)isthe The discovery of the CIB (Puget et al. 1996; Fixsen et al. third generation space mission to measure the anisotropy of the 1998) has added to the importance of our understanding of cosmic microwave background (CMB). It observes the sky in nine frequency bands covering 30–857 GHz with high sensitiv- dust in galaxies. The CIB demonstrates that roughly 50% of   all energy generated in the history of the Universe was ab- ity and angular resolution from 31 to 5 . The Low Frequency sorbed by dust and reprocessed into the FIR/submm (Gispert Instrument LFI; (Mandolesi et al. 2010; Bersanelli et al. 2010; et al. 2000). Deep surveys at 850 μm with SCUBA (e.g., Smail Mennella et al. 2011) covers the 28.5, 44.1, and 70.3 GHz bands, et al. 1997; Hughes et al. 1998; Eales et al. 2000; Coppin et al. with amplifiers cooled to 20 K. The High Frequency Instrument 2006) and at nearby wavelengths with other instruments (e.g., (HFI; Lamarre et al. 2010; Planck HFI Core Team 2011a)cov- MAMBO, AzTEC and LABOCA, Weiß et al. 2009; Austermann ers the 100, 143, 217, 353, 545, and 857 GHz bands, with . et al. 2010) have revealed much higher number counts than bolometers cooled to 0 1 K. Polarization is measured in all but would be predicted by a non-evolving extrapolation of the lo- the highest two bands (Leahy et al. 2010; Rosset et al. 2010). cal population. There must thus be very rapid evolution of the A combination of radiative cooling and three mechanical cool- FIR/submm galaxy population, something confirmed by obser- ers produces the temperatures needed for the detectors and op- vations with ISO, (e.g., Dole et al. 2001) Spitzer (e.g., Frayer tics (Planck Collaboration 2011b). Two data processing centers et al. 2006; Béthermin et al. 2010; Clements et al. 2010a)and (DPCs) check and calibrate the data and make maps of the sky Planck BLAST (Devlin et al. 2009). Herschel observations have now (Planck HFI Core Team 2011b; Zacchei et al. 2011). ’s confirmed this rapid evolution through a combination of number sensitivity, angular resolution, and frequency coverage make it a count (Clements et al. 2010c; Oliver et al. 2010) and luminos- powerful instrument for Galactic and extragalactic astrophysics ity function (Dye et al. 2010; Eales et al. 2010b; Dunne et al. as well as cosmology. Early astrophysics results are given in 2011) studies. However, detailed interpretation of these results Planck Collaboration (2011h–z). is hampered by our poor knowledge of galaxy SEDs in the 100– 1000 μm range. This is demonstrated, for example, by the result 2.2. The Planck early release compact source catalogue that IRAS-selected galaxies and high redshift SCUBA-selected SMGs (e.g., Clements et al. 2010b) lie in separate parts of the The Planck ERCSC (Planck Collaboration 2011c) provides po- temperature-luminosity diagram (e.g., Clements et al. 2010b; sitions and flux densities of compact sources found in each of Symeonidis et al. 2009). The origin of this separation is un- the nine Planck frequency maps. The flux densities are cal- clear. It might represent a genuine change in dust temperature culated using aperture photometry, with careful modelling of with redshift, and selection biases may be partly involved, but it Planck’s elliptical beams. The colour corrections for sources α could also reflect our ignorance of the full FIR/submm SED of with spectral index α = −0.5 (using the convention S ν ∝ ν ) local galaxies. By properly establishing a zero redshift baseline are 1.017, 1.021 and 1.030, respectively, for the 28.5, 44.1, and for the dust SEDs of typical galaxies, the Planck ERCSC will 70.3 GHz LFI channels. Flux densities taken from the ERCSC allow the origins of the CIB and the nature of the galaxies that should be divided by the appropriate colour correction to give contribute to it to be much better determined. the correct flux values for an assumed narrow band measure- The central goals of this paper are thus twofold: to exam- ment at the central frequency. For frequencies from 28.5 to ine the properties of a large sample of local (z < 0.25) galaxies 143 GHz, compact sources have been detected using a version of the “Powell Snakes” techniques (Carvalho et al. 2009); for details see Planck Collaboration (2011c). In the four higher 1 Planck (http://www.esa.int/Planck) is a project of the European Space Agency (ESA) with instruments provided by two sci- frequency channels, sources were located using the SExtractor entific consortia funded by ESA member states (in particular the lead package (Bertin & Arnouts 1996). Sources detected in one or countries France and Italy), with contributions from NASA (USA) and more of the frequency maps were then put through a further telescope reflectors provided by a collaboration between ESA and a sci- set of secondary selection criteria; these are discussed in detail entific consortium led and funded by Denmark. in Planck Collaboration (2011c). The primary criterion utilized

A16, page 2 of 16 Planck Collaboration: Planck early results. XVI. was a Monte Carlo assessment designed to ensure that ≥90% of the sources in the catalogue have a flux accuracy of at least 30%. For this paper we are primarily interested in the sources se- lected in the 857 GHz (350 μm) band, the catalog of which also includes bandmerged fluxes for each 857 GHz detected source in the next three highest Planck bands i.e. 545 GHz, 353 GHz, and 217 GHz (∼550 μm, 850 μm and 1300 μm respectively). The Planck beam is 5 in all these bands and all sources are detected in the 857 GHz band with at least 5σ significance. This does not translate into a single fixed flux limit, however, because of the effects of foreground extended emission and the details of the Planck scanning strategy which mean that some parts of the sky (e.g. the ecliptic poles) are scanned more often than others.

2.3. Matching the ERCSC to IRAS data To understand the FIR Spectral SEDs we need a combination of data at long wavelengths, provided by the Planck ERCSC, and data near the peak of a typical galaxy dust SED at about 100 μm. The best source for the latter information is the IRAS all-sky FIR survey, and the most recent analysis of the IRAS Fig. 1. Histogram of offsets between ERCSC and IIFSCz positions. Faint Source Catalogue (FSC) is provided by Wang & Rowan- Robinson (2009) in the Imperial IRAS FSC redshift survey (IIFSCz). This was constructed using IRAS FSC sources, all of which are at |b| > 20◦, with IRAS colours used to exclude inspection of the Sky Survey postage stamps provided in NED. and cirrus sources (with S (100)/S (60) > 8). The NASA Associations were accepted as real if the associated galaxy had Extragalactic Database (NED) was then used to find spectro- ablue(g or B) magnitude brighter than 16. The surface-density scopic for the resulting FSC source list, and to as- of such galaxies leads to the probability of a chance associa- tion being ∼3%. For sources where there was both an IRAS sociate the sources with SDSS (where available; York et al. = 2000) and 2MASS (Skrutskie et al. 2006) galaxies to find and a 2MASS association, this limit was relaxed to B 17 (or K ∼ 13). Of the 88 ERCSC-IIFSCz associations with po- photometry at 0.36–2.2 μm. This photometry was then used ff  to estimate photometric redshifts for sources without spectro- sitional o sets 3–5 (and with spectroscopic or photometric red- scopic redshifts. A full description of the photometric method shifts) 72 were associated with bright galaxies, two were asso- used and the accuracies obtained for this work is included in ciated with a second FSC source having cirrus-like colours and Wang & Rowan-Robinson (2009). are presumed to be cirrus, and the remaining 14 are classified as The starting point for matching the ERCSC to the IIFSCz possible galaxy associations (these are excluded from the reli- is the set of 9042 sources detected at 857 GHz (350 μm) by able galaxy catalogue used here for further analysis). Planck. This is then restricted to the 5773 sources at |b| > 20◦ for The second category of ERCSC-IIFSCz associations which which there will be FSC data. Associations of ERCSC sources we scrutinised in detail were those for which there is no redshift with IIFSCz were looked for using a search radius of 5.The in the IIFSCz. There were 165 of these and the NED associ- histogram of positional offsets is shown in Fig. 1.Thebulk ations suggest that 38 are bright galaxies, seven are cirrus, two of associations have offsets within 2.Evenat5 there is no are bright planetary nebulae, and the remaining 118 are classified steep increase in the number of associations which would be in- as possible galaxy associations (and excluded here). We were dicative of a large fraction of chance associations. On the ba- left with 1717 reliable ERCSC-IIFSCz galaxy associations of sis of source surface-density, the chance of a random associ- which 337 are flagged as extended in the ERCSC. 1597 of these ation with an IIFSCz source within 3 is 1.6%, and within 5 1717 objects have spectroscopic redshifts. None of the sources it is 4.5%. A total of 1966 associations were found within 5. with photometric-only redshifts or possible multiple identifica- There were 106 cases where an ERCSC source picked up an tions are used in the subsequent SED analyses in this paper. association with more than one IIFSCz source within 5.Weex- amined these cases carefully to ensure that only a single asso- 2.4. ERCSC sources not associated with IIFSCz sources ciation was accepted. Generally the nearer association was pre- ferred. Where the offsets of the two associations were compara- Figure 2 shows the sky distribution of ERCSC sources at |b| > ◦ ble, the brighter IRAS source was preferred. There are 20 cases 20 , with sources flagged as extended in the ERCSC shown where two bright galaxies less than 5 apart have generated a as blue filled hexagons, and point-sources shown in black. single ERCSC source, for which there may be a significant con- Associations with the IIFSCz are shown as red circles. The tribution from both galaxies to the ERCSC flux. These confused extended sources not associated with IIFSCz sources have a sources would benefit from additional observations with ground- strikingly clustered distribution, which matches the areas of based submm instruments to determine the contribution of each our Galaxy with strong cirrus emission, as evidenced by IRAS component to the submm emission detected by Planck. 100 μm maps and by the ERCSC cirrus flag (values >0.25). We The remaining ERCSC-IIFSCz associations were further presume the majority of these are cirrus sources and not extra- scrutinised as follows. Firstly, for sources with positional offsets galactic. between the two catalogues in the range 3–5 all NED associa- To test this further, we looked for NED associations with tions within 5 of the ERCSC positions were examined to test the all 444 extended ERCSC sources lacking IIFSCz associations validity of the association with the IRAS source. This included (i.e. are within 5)at|b| > 60◦. Only 12 were found to have

A16, page 3 of 16 A&A 536, A16 (2011)

Fig. 2. Sky plot of ERCSC sources in galactic coordinates. Black filled hexagons are ERCSC point-sources and blue filled hexagons are ERCSC sources flagged as extended. Red hexagons are sources associated with IIFSCz IRAS FSC galaxies, after scrutinising suspect categories with NED (and excluding some, as described in the text). Green hexagons are ERCSC sources not associated with IIFSCz, but associated with bright galaxies in NED (only for |b| > 60◦ for extended sources). associations with bright (b, g<16) galaxies. Extrapolating to Some of these 419 sources are almost certainly fainter galaxies, |b| = 20–60◦,weestimatethatafurther∼50 of these extended although many could turn out to be cirrus. Improved submm or non-FSC sources will be bright galaxies. The remainder of the FIR positions are needed, either via Herschel or ground-based 3431 extended non-FSC sources at |b| > 20◦ are presumed to be telescopes, to identify these sources reliably. Galactic cirrus. Following this identification analysis we restrict ourselves to A ridge of non-FSC point sources can be seen in Fig. 2 those galaxies with reliable IIFSCz associations and with de- at b ∼ 70◦, l ∼ 120–230◦. These correspond to one of the tections in the 857 and 545 GHz bands at significance of 5σ IRAS coverage gaps. We examined NED associations for all or greater, as well as detections in the 353 GHz band of 3σ or 482 ERCSC point-sources not associated with IIFSCz sources. greater. This amounts to a total sample size of 595 galaxies. 32 were found to be associated with Local Group galaxies (M 31, SMC and WLM, with 28 in the LMC), 123 are bright galaxies, 2.5. Cirrus contamination 27 are associated with IRAS FSC or PSC Galactic cirrus sources, and 10 are bright stars or planetary nebulae. Most of the bright Our analysis of the non-IIFSCz-identified ERCSC sources in galaxies lie in the IRAS coverage gaps. The remaining 289 are Sect. 2.4 led us to the conclusion that sources which are extended classified as possible galaxy associations (and excluded here). in the ERCSC are a result of cirrus structure in our own Galaxy, To summarise, we have found a net total of 1884 definite or at best are a combination of cirrus structure with flux from a associations with galaxies. These constitute an ERCSC galaxy galaxy. Of the 595 reliably detected IIFSCz-identified ERCSC catalogue. A further 419 sources are not associated with bright sources, 127 are listed as extended in the ERCSC. We test these galaxies, but there are grounds for thinking they could be extra- objects for the possibility of cirrus contamination by examin- galactic sources. Some have IIFSCz associations, but there are ing the amplitude of the local cirrus fluctuations in the 100 μm too many possible faint optical or near-IR galaxy counterparts to cirrus maps of Schlegel et al. (1998). We adopt this approach be confident which might be associated with the ERCSC source. since regions of greatest cirrus fluctuation are those most likely

A16, page 4 of 16 Planck Collaboration: Planck early results. XVI.

Fig. 4. Colours for the ERCSC galaxies (black dots) compared to those Fig. 3. 60 μm to 857 GHz (i.e., 350 μm) colour plotted against the cirrus found for SLUGS galaxies (red; Dunne & Eales 2001; Vlahakis et al. RMS at 100 μm in IRAS. ERCSC sources classified as point-like are 2005) and ULIRGs (blue; Clements et al. 2010b). A flux correction shown as open diamonds, while extended sources are shown as solid factor of 0.506 has been applied to the Planck 857 GHz (350 μm) flux dots. Note that the extended sources show a clear correlation between densities to extrapolate them to the SCUBA 450 μm band. This correc- colour and cirrus RMS, indicating that these sources are likely to be tion is appropriate for sources with the SLUGS median galaxy SED contaminated by cirrus emission. i.e. T = 35 K and β = 1.3, but this factor will be similar for most reasonable dust SEDs. Only sources detected at >3σ in the 353 GHz (850 μm) band and at >5σ in the 857 GHz (350 μm) band (the require- to cause problems for point source detection in the ERCSC. We ment for inclusion in our analysis) are shown. The four points above measure the cirrus RMS in a 3 × 3 array of points, separated by the general trend in the lower left of the diagram are bright non-thermal 0.1◦ and centred on the position of the ERCSC source. Since cir- dominated sources 3C 279, [HB89]0537−441, OJ+287 and 3C 273. The SLUGS point with the lowest 60 μm to SCUBA flux ratios corresponds rus emission is likely to have cooler FIR-to-submm colours than ff the integrated emission of an external galaxy, we then look for to the galaxy IC 979; it is o set from the general correlation for SLUGS and ERCSC galaxies, and Vlahakis et al. (2005) note that its IRAS flux any correlation between cirrus RMS and the 60 μm-to-857 GHz densities should be treated with caution. colour. We plot this relation in Fig. 3. As can be seen from Fig. 3, there appears to be a correla- tion between colour and cirrus RMS for the sources classified as extended in the ERCSC. We conclude that the ERCSC fluxes allowing for the existence of a second, cooler, dust component for these sources are partially contaminated with cirrus emission to be assessed. For these objects, and more recently for an ultra- from our own Galaxy. We thus exclude these 127 sources from luminous IR galaxy (ULIRG) sample, Dunne & Eales (2001) further analysis. Of the remaining 468 non-extended ERCSC and Clements et al. (2010b) found some evidence for a colder sources, fewer than 10 lie in the region of this correlation. These dust contribution. sources are retained for the following analysis, but any conclu- The presence of colder dust can be inferred from colour- sions that come solely from these specific sources will be treated colour diagrams when two submm flux densities are available. with caution. We show the SLUGS sources and the ERCSC sources (af- More generally, this analysis highlights one of the issues that ter colour corrections to the Planck flux densities and a suit- must be faced when using the ERCSC catalogue. Anyone wish- able scaling has been applied to convert from Planck 857 GHz ingtocross-matchPlanck sources, especially those detected at flux density to the SCUBA 450 μm band) in Fig. 4. As can high frequencies, with sources at other wavelengths, needs to be seen, the Planck galaxies lie on the same broad trend as take great care in ensuring that the ERCSC fluxes are not con- the SLUGS galaxies (with the exception of a small number taminated by cirrus emission. of objects dominated by a non-thermal AGN component, such as 3C 273 and 3C 279). The ERCSC sources, though, extend the trend to cooler FIR/submm colours than were found for 3. Comparison to existing submm data the SLUGS objects, suggesting that the galaxies detected in the ERCSC contain cooler dust than was detected in the majority of 3.1. Galaxies detected with SCUBA SLUGS sources. The largest studies of cool dust in external galaxies to date have been associated with the SCUBA Local Universe Galaxy Survey 3.2. CO contamination (SLUGS) and its extensions (Dunne et al. 2000; Dunne & Eales 2001; Vlahakis et al. 2005; Clements et al. 2010b). These en- One factor that has complicated the interpretation of ground- compass a total of about 250 objects that were observed with based submm observations of galaxies has been the presence SCUBA. The targets were selected on the basis of IRAS flux of CO emission lines within the submm passbands that make B-band optical magnitude or FIR luminosity. Most of the ob- a significant contribution to the continuum flux. Seaquist et al. jects were detected only at 850 μm (i.e., not also at 450 μm), (2004) estimated that the CO (3–2) line contributed an aver- allowing, with the IRAS data, only a single component (T,β) age 25% of the flux received in the SCUBA 850 μm contin- β fit – where the SED is described as S ν ∝ ν B(ν, T), with B(ν, T) uum passband for galaxies observed in the SLUGS survey, with being the Planck function, and the parameters T and β repre- the range of flux contributions going from 10–45% for the sub- senting temperature and dust emissivity index, respectively. A set of SLUGS galaxies for which CO(3–2) observations were small fraction of SLUGS galaxies were also detected at 450 μm, available. The SCUBA 850 μm filter has a bandwidth of

A16, page 5 of 16 A&A 536, A16 (2011)

∼30 GHz. The Planck 353 GHz (850 μm) filter is significantly In these equations, A or Ai is an overall amplitude for each com- broader, at ∼90 GHz, so the line contribution will be corre- ponent, and the factor of (1 + z) converts from rest-frame fre- spondingly smaller at ∼8% on average. The broad Planck pass- quency to observed frequency for an object at redshift z.The band also means that CO(3–2) is a potential contaminant over a noise contribution is given by nν, which we model as a Gaussian 2 broader redshift range than for ground based studies, with con- with variance σν.ForthePlanck channels, the determination tamination possible from z = 0 out to z = 0.15, which essen- of the noise contribution is described in Planck Collaboration tially encompasses all of the galaxies discussed in this paper. (2011c). For IRAS, the detections are classified in the IIFSCZ of This CO contamination fraction can be checked using observed Wang & Rowan-Robinson (2009) into (1) good detections, for values of integrated CO 3–2 line fluxes for a variety of objects which we take σν = 0.1dν; (2) marginal detections, for which from Bayetetal.(2006) and matching them to continuum ob- we take σν = 0.5dν; and (3) upper limits, for which we take σν servations of similar beamsize to the CO observations. We find derived from the reported upper limit, and dν = 0. As mentioned contamination fractions of 2% for Arp 220, 6% for Mrk 231 and above, we only consider sources with detections in the 857 and a worst case example in the central region of NGC 253, where a 545 bands at significance of at least 5σ or greater and in the contamination of 11% is calculated. This level of contamination 353 band of at least 3σ. in a real object is unlikely since we this tacitly assumes that the Thus, the parameters of our model are some subset of the CO and continuum emission have matching spatial extent, while Ai, Ti,β, depending on which model we fit. We use a Bayesian in a real object the continuum emission is likely to be more ex- Markov Chain Monte Carlo (MCMC) (e.g., Lewis & Bridle tended than CO, leading to a smaller fraction of CO contamina- 2002; Jaynes 2003) technique to probe the parameter space; with tion. our Gaussian noise, this is equivalent to an exploration of the We can extend this analysis to other Planck bands using χ2 surface, albeit with a nonlinear parameterization. We require NGC 253 as a worst case since, unlike most others, this object a0≤ β ≤ 3and3K≤ T ≤ 100 K with a uniform prior proba- has been observed over the full range of CO transitions acces- bility between those limits (detections of very low temperatures, sible from the ground. We find that the higher frequency bands T < 10 K, are actually dominated by non-thermal emission). We have a reduced level of contamination compared to the 353 chan- adopt a uniform prior on ln Ai, as it ranges over many orders of nel, with <1% at 857 (350 μm) and 6% at 545 (550 μm), assum- magnitude for sources of widely varying absolute luminosities ing a flat spectral line energy distribution to estimate the contri- and distances. bution of the CO 5–4 line that is inaccessible from the ground. The MCMC engine first creates a 15 000-sample Markov More normal objects than NGC 253, not dominated by an on- chain, varying one parameter at a time, using this to find going starburst, will have an even smaller level of CO contam- an approximately-orthogonal linear combination of parame- ination than this. At lower frequencies, though, the contamina- ters, with which a subsequent 100 000-sample chain is run. tion can become more serious. CO 2–1 could contribute as much Convergence is assessed by re-running a small number of chains as 21% of the continuum flux in the 217 band in the inner re- from a different starting point and checking for agreement to gions of NGC 253 and as much as 75% in the 100 band. The much better than one standard deviation in all parameters. inner regions of NGC 253 are very much a worst case scenario, We calculate an approximation to the Bayesian evidence, or so more typical sources would of course suffer much less con- model likelihood (Jaffe 1996; Jaynes 2003) in order to compare tamination. However, very few galaxies are detected by Planck the two-temperature and one-temperature fits. The evidence is solely in thermal emission in this band, and the few that are de- calculated as the average of the likelihood function over the prior tected are bright nearby objects with substantial archival data distribution; we approximate the likelihood as a multivariate that can allow a direct assessment of the CO contribution (Peel Gaussian function of the parameters centred at the maximum- et al., in prep.). likelihood MCMC sample with covariance given by the empir- Our conclusion from this analysis is that the CO contribution ical covariance of the samples (this approximation ignores the to the continuum flux is likely to be smaller than other sources of prior on the amplitude of the individual grey bodies). uncertainty for generic ERCSC-detected galaxies except for the In Figs. 5, 6 we show sample output from our MCMC runs small number which are detected in the 217 band. Flux excesses for different objects and models, along with the measured SEDs detected in this band alone might thus result from CO emission and fits. For objects such as F00022-6220 in Fig. 5,ifwein- rather than from any putative very cold dust component. stead perform a two-temperature fit, it prefers the amplitude of the second temperature component to be many tens of orders of 4. Parametric models of dust SEDs magnitude below the first, and gives temperature values consis- tent with the one-temperature fit; this indicates, along with the 4.1. Fitting method approximate evidence discussed above, that a one-temperature Given the Planck and IRAS flux data described in Sect. 2, with model is strongly preferred. appropriate colour corrections applied to the Planck flux densi- ties, we model the underlying signal in observed frequency band 4.2. Results from parametric fits ν as one or more grey-body sources with flux density β 4.2.1. Single component fits G(ν; T,β) ∝ ν Bν(T), (1) Figure 7 shows the T − β plane for parametric fits to all 468 reli- where B (T)isthePlanck function for blackbody flux density. ν ably identified non-extended sources within the ERCSC-IIFSCz We fit the data d to one-component models of the form ν cross match whose flux densities pass our S/N ratio criteria dν = AG[ν(1 + z); T,β] + nν, (2) for inclusion, together with similar single temperature paramet- ric fits from Dunne et al. (2000)andClements et al. (2010b). or to two-component models with a fixed β = 2 grey-body expo- As can be seen, the Planck ERCSC sources overlap with the nent (e.g. Dunne & Eales 2001), SLUGS galaxies but extend to cooler temperatures and flat- dν = A1G[ν(1 + z); T1, 2] + A2G[ν(1 + z); T2, 2] + nν. (3) ter, i.e., lower β, SEDs. The median parameters for the Planck

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Fig. 5. Left panel: samples from the SED likelihood function (χ2) for F00022-6220 and the one-temperature model. The bottom row shows the one-dimensional (marginalized) posterior for the parameters (log A, β, T), and the other panels show all two-dimensional marginal distributions. Right panel: the data points for this object, along with the one-temperature model for the maximum likelihood sample (yellow curve; T = 33.0, K, β = 1.25) and the model determined by the mean of the samples of each parameter (red curve; T = (33.2 ± 4.8) K, β = 1.25 ± 0.42 where the errors are the standard deviations). Note the logarithmic axes which make interpretation of the error bars difficult.

Fig. 6. As in Fig. 5, but for F00322-0840 and the two-temperature model with fixed β = 2. The maximum-likelihood temperatures are 20 K and 49 K the means and standard deviations are (20 ± 0.8) K and (44 ± 8) K. sources are T = 26.3 K with temperatures ranging from 15 The position of our galaxies in the Luminosity-Temperature to 50 K, and β = 1.2 compared to corresponding values from plane is an important question since it relates to claims of evo- 104 SLUGS galaxies Dunne et al. (2000)ofT = 35 K and lution in the dust properties of galaxies. It has previously been β = 1.3 and of T = 41 K and β = 1.6 for 26 ULIRGs Clements suggested that high redshift, high luminosity SMGs have lower et al. (2010b). This confirms the result from consideration of dust temperatures and higher dust masses than more nearby ob- Planck-IRAS colours in Fig. 4 that we are seeing cooler dust in jects (Yang et al. 2007). Comparison of SMGs from Chapman the ERCSC-IIFSCz galaxies. et al. (2005), Coppin et al. (2008)andKovács et al. (2006) with There are ten sources common to the ERCSC-IIFSCz cross- more local galaxies from Dunne et al. (2000) and local ULIRGs matched catalogue and the SLUGS studies. The fits using Planck Clements et al. (2010b) confirms this effect. Claims have been data and using SLUGS data for all but two of these sources made that sources selected at longer wavelengths than the 60 μm are in good agreement. The two exceptions are NGC 7541 typical of IRAS derived samples (e.g., Symeonidis et al. 2009; and NGC 5676. The likely cause of the disagreements in these Patel et al., in prep.) show less of a separation between the lo- cases, is the presence of a close companion IRAS source to cal sources and the higher redshift SMGs. Much of this work is NGC 7541 (NGC 7537 3.1 separation, and thus only ∼0.7 beam hampered by the poor sampling of the dust SEDs of local objects FWHM away), so that the Planck flux density is likely over- at wavelengths between 100 and 850 μm. Recent results from estimated, and extended IRAS emission in NGC 5676, making Herschel (Amblard et al. 2010)andBLAST(Dye et al. 2009) the IRAS FSC flux densities used in our analysis underestimates. have begun to fill the gap between local IRAS galaxies and the

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Fig. 7. Temperature-β correlation for ERCSC-IIFSCz matched galaxies Fig. 8. The Temperature-Luminosity plane showing a variety of FIR (solid dots) together with data from Dunne et al. (2000)andClements populations. Open squares are SMGs from Chapman et al. (2005), open et al. (2010b) for SCUBA observed sources (triangles and squares re- triangles are SMGs observed with SHARCII by Coppin et al. (2008) spectively). The four sources with β = 0andT < 10 K at the left of and Kovács et al. (2006). + signs are the SLUGS sources from Dunne the diagram are the non-thermal dominated sources 3C 279, 0537-441, et al. (2000), × are intermediate redshift ULIRGs from Yang et al. OJ+287 and 3C 273. (2007), ULIRGs from Clements et al. (2010b) are open circles. Planck- ERCSC-IIFSCz galaxies are shown as solid dots. As can be seen the previous apparent distinction between the local FIR populations and the SMGs is weakened by sources from this work lying in the same region SMGs, suggesting that our view of dust temperatures in local as the SMGs and by filling in some of the gap between the populations. objects are biased to warmer temperatures through our depen- The four aberrant sources with T < 15 K and high L in the bottom right dence on IRAS flux densities. In Fig. 8 we show the positions of of the plot are the non-thermal dominated sources 3C 279, 0537-441, Planck galaxies on the L − T plane, where the far-IR luminosity OJ+287 and 3C 273. is calculated by integrating the luminosity of the fitted dust SED over the range 8–1000 μm. As can be seen, the gap between the local galaxies and the SMGs is starting to be filled by the as seen by COBE (Reach et al. 1995). We investigate this by Planck objects. The Planck fluxes for one of these sources may applying two component fits to the dust SEDs. include some contamination from cirrus, but the rest lie in areas of normal to low Galactic cirrus noise and should thus be fully 4.2.2. Two temperature fits reliable. The large area coverage of Planck is particularly impor- tant in this as it allows us to probe generic L/ULIRG-class ob- We carry out two temperature component fits on our sources, as- 11 jects (LFIR > 10 L ) rather than having to rely on pre-selected suming β = 2 for both components, and present the temperature- IRAS bright sources as in Clements et al. (2010b). Herschel ob- temperature plot in Fig. 9. We also use the Baysian evidence servations, which are also beginning to show the gap being filled, calculated during the fitting process (Jaffe 1996; Jaynes 2003) do not yet cover enough area to include many such L/ULRG ob- to determine how many of our sources show evidence for a two jects in the local Universe (Amblard et al. 2010). We find several component fit above that of the single component (T,β)fit.We cool (T < 30 K) ULIRGs that have very similar characteristics find that the two component fit is favoured in most cases, with to SMGs. The issue of the apparent distinction between local 425 objects giving a higher evidence for this model and only galaxies and the high-z SMG population thus seems to be ap- 43 preferring the single component fit. Once again we test the proaching resolution. possibility that issues with the lower significance 353 GHz flux While the temperature distribution of our objects is consis- densities might bias these fits by repeating the analysis with tent with what has been seen elsewhere, we find that some of these fluxes excluded. While this increases the uncertainties in our galaxies have β more than 3σ less than 1. One possible the fits, as with the (T,β) fits we find that the exclusion of the cause for this might be the 353 GHz flux density being affected 353 GHz fluxes makes no systematic difference to the tempera- by Eddington bias (see e.g., Teerikorpi 2004), leading to “flux- tures found. We find clear evidence for a second dust tempera- boosting” of lower significance detections, since we accept these ture component in most of the objects in the sample, with a mean fluxesdownto3σ. This is tested by repeating the fits using only Tcold = 16 ± 4KandTwarm = 36 ± 9K. the IRAS, 857 and 545 GHz flux densities. While there are small We find 17 galaxies fit by models containing a dust com- differences in fits to individual objects resulting from the exclu- ponent with temperatures as low as 10 K. Four of these are the sion of the 353 GHz flux densities, the general distribution re- bright blazars and are thus dominated by non-thermal emission, mains the same, complete with the low β sources. We thus con- while one is a source that might still contain some cirrus con- clude that this is a real effect and not due to Eddington bias or any tamination. We thus find at least 13 galaxies which appear to other issue related to the 353 GHz flux densities, such as con- contain very cold dust. Such dust has previously been found in tamination by emission from the CO 3–2 molecular line. While our own galaxy (e.g. Reach et al. 1995), has been suggested in a such low β values are not expected in simple models of dust, it is small number of dwarf galaxies (Galliano et al. 2005; Galametz suggestive that the SEDs can be better fit by a parameterization et al. 2009) and in a small number of spiral galaxies observed that uses a mixture of dust at two temperatures, as suggested by by SCUBA (Stevens et al. 2005). The current work is the first Dunne & Eales (2001) and which is a good fit to our own galaxy time it has been seen before in a large scale extragalactic survey.

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quantities of cold dust in some galaxies Rowan-Robinson et al. (2010). The Rowan-Robinson et al. (2010) study of the SEDs of Herschel-detected galaxies used SPIRE flux densities extend- ing from 250 to 500 μm combined with pre-existing data from SWIRE at Spitzer and optical wavelengths. Through the combi- nation of Planck data with the IIFSCz, the galaxy sample con- sidered here includes data from the optical to IRAS fluxes, and then the Planck data has flux densities at 350, 550 and 850 μm (857, 545 and 353 GHz). Some of our objects are also detected at 1.4 mm (217 GHz) which is included in our analysis if available. The range of wavelengths available with the ERCSC-IIFSCz sample is thus broader than that available through Herschel.This enables us to place better constraints on the role and importance of cold dust in these objects. Our sample is also much larger than the 68 objects considered in Rowan-Robinson et al. (2010), so we can better determine the variety and overall statistics of Fig. 9. The Temperature-Temperature plane for two temperature com- the SEDs of local galaxies. ponent fits for ERCSC-IIFSCz matched galaxies. together with data The templates used in fitting IRAS (Rowan-Robinson 1992), from Dunne & Eales (2001)andClements et al. (2010b) for SCUBA ob- ISO (Rowan-Robinson et al. 2004)andSpitzer (Rowan- served sources (triangles and squares respectively). Only those ERCSC- Robinson et al. 2008), data are (1) a cirrus (optically thin IIFSCz sources where the two temperature model is preferred and with interstellar dust) model characterised by a radiation intensity a reliably determined cold dust component temperature (i.e., T/σ(T) > φ = I(galaxy)/I(ISRF) = 5, where I(ISRF) is the intensity 4) are plotted. The sources with the coldest Tcold < 7 K in this plot are dominated by non-thermal emission. of the radiation field in the solar neighbourhood; (2) an M 82- like starburst; (3) a higher optical depth Arp220-like starburst; (4) an AGN dust torus. In fitting the SEDs of Herschel galax- ies, Rowan-Robinson et al. (2010) use two further cirrus tem- Other explanations for these “submm excess” sources have been plates with φ = 1 and 0.1, which correspond to significantly suggested, especially in the context of low metallicity galaxies cooler dust than in the standard cirrus template. The starting where changes in the emissivity as a function of wavelength have point for the present analysis is the template fit for each ob- been suggested. The small number of sources which have Tcold ject given in the IIFSCz Catalogue (Wang & Rowan-Robinson lower than 7 K are all dominated by nonthermal emission. The 2009) and discussed in Wang & Rowan-Robinson (2010). This details of the temperature-temperature plot in Fig. 9, with small was done by fitting the optical and near-IR fluxes with an opti- scatter and the temperature of the hot component being largely cal galaxy or QSO template. The IRAS data were then fitted with independent of that of the cold component up to Tcold ∼ 18 K one of the original four Rowan-Robinson et al. (2008) templates. will likely have implications concerning the relationship be- This model is then compared to the Planck data. In almost all tween hot and cold dust components. cases additional components are needed, since the IRAS-based predictions underestimate the submm flux densities provided by Planck. The fits are not always good at 353 and 217GHz. 4.3. The broader ERCSC-IIFSCz sample This may be a combination of Eddington bias due to the poorer The parametric fitting reported here only concerns the 468 non- signal-to-noise at this frequency, or CO contamination. extended ERCSC-IIFSCz matched galaxies which are detected at 5σ or greater in the 857 and 545 GHz bands and at 3σ or 5.1. Results from template fits greater at 353 GHz. This ensures that uncertainties in the fluxes do not preclude a good fit to the SED, but brings the risk that we In Fig. 10 we analyze the SEDs of the archetypal nearby galax- might be missing a significantly different subclass of object in ies, M 51, M 100, M 2 and Arp 220. M 51 and M 100 are mod- the remaining 1122. We have thus applied our fitting methods to elled with two cirrus templates with φ = 1 (solar neighbour- this whole sample, regardless of ERCSC S/N beyond the basic hood) and 5 (Galactic Centre), and with a modest M 82 starburst detection requirement of a 5σ or greater detection at 857 GHz. component. M 82 itself needs an additional component of cool While there are larger errors bars on the fitted parameters we find cirrus (φ = 1) as well as the M 82 template of Efstathiou and no indication that galaxies in this larger sample have a different Rowan-Robinson (Efstathiou & Rowan-Robinson 2003). Finally range of dust properties to those discussed above. Arp220 is modelled extremely well over all infrared and submm wavelengths by the Arp220 template used by Efstathiou and Rowan-Robinson. The models for these galaxies by Silva et al. 5. Physical models: template fitting (1998) are also shown and perform well, especially for M51 and Arp 220. The FIR and submm spectral energy distributions of galax- Figure 11 shows fits to galaxies with detections in 16 pho- ies from the IRAS, ISO and Spitzer surveys have been tometric bands: 5 optical bands (SDSS), 3 near infrared bands successfully modelled with a small number of templates (2MASS), 4 mid and FIR bands (IRAS) and 4 submm bands (Rowan-Robinson 1992; Rowan-Robinson et al. 2005; Rowan- (Planck). The blue curve is the solar neighbourhood cirrus tem- Robinson et al. 2008). However the submm data available in plate (φ = 1) and contributes significantly to the SEDs of 7 out such studies is quite limited and we expect to get a much bet- of the 8 galaxies. Dust grains in this component are in the range ter understanding of cool dust in galaxies with the data from 15–20 K, depending on grain radius and type (Rowan-Robinson 7 8 Planck. Already with Herschel, there is evidence for unexpected 1992). Dust masses are in the range 10 −3 × 10 M .

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Fig. 10. Template fits for the four archetypal nearby galaxies, M 51, M 100, M 82 and Arp 220. Black curves: fits with Efstathiou and Rowan-Robinson templates (black, separate components as dotted lines), blue curves: Silva et al. (1998) models. Planck ERCSC data shown as red filled hexagrams. ISO-SWS mid-infrared spectroscopy data for M 82 and Spitzer-IRS data for Arp 220 (Siebenmorgen & Krügel 2007)are shown in magenta.

To get an overview of the whole sample, Fig. 12 shows the and good optical data (Fig. 14). This list includes four of the distribution of 545 GHz (550 μm) flux density versus redshift for galaxies identified as having cold dust on the basis of parametric galaxies well detected at 350–850 μm, and with spectroscopic SED fitting above, the remainder of which do not have the redshifts. The loci of galaxies with an Arp 220 template at lu- full range of optical data necessary for this approach. Almost 12 13 minosity LIR = 10 and 10 L are shown. With the restric- all require the very cold cirrus model with Tdust = 10–13 K, tions to point-sources with good detections in the three highest φ = 0.1 (green curves in Fig. 14). Table 1 gives the properties frequency Planck bands, and to galaxies with spectroscopic red- of the galaxies whose SEDs we have modelled in detail. We shifts, a number of ULIRGs are found in the ERCSC survey, but can summarize the SED modelling shown in Figs. 10, 11 and no HLIRGs, apart from the quasar 3C 273. 14 as follows: (1) most nearby galaxies show evidence for dust at temperatures similar to that seen in the solar neighbourhood Figure 13 shows the colour-ratio S 857/S 545 (i.e. = / (φ 1), as well as the warmer dust found in IRAS, ISO and 350 μm 550 μm) versus redshift. Galaxies in the IRAS Spitzer studies; (2) there is a new population of cool submm Bright Galaxy Sample are indicated as red dots. Sources for galaxies with even cooler dust (φ = 0.1, Tdust = 10–13 K). This which T2 < 10 K in the 2-temperature fits discussed above are cooler dust is likely to have a more extended spatial distribution indicated as blue dots. Sources with log10(S 857/S 545) < 0.4 then generally assumed for the gas and dust in galaxies. represent a novel population of cooler submm sources that have only previously been hinted at (Stevens et al. 2005). This plot also demonstrates a method of selecting galaxies containing 6. Conclusions cold dust that is complementary to the parametric SED fitting process discussed in Sect. 4. We have modelled all 17 galaxies Our studies of nearby galaxies detected by Planck confirm the with cool 857 GHz/545 GHz colours (log10(S 857/S 545 < 0.4), presence of cold dust in local galaxies, something that has A16, page 10 of 16 Planck Collaboration: Planck early results. XVI.

Table 1. Parameters for Planck ERCSC-IIFSCz galaxies with SED fits.

RA Dec FSS dist zspect log (L)log(L)log(L)log(L)log(L)log(L) type AV log (M∗)log(Mdust) cirr cirr cirr SB Arp220 Opt M M ψ = 5 ψ = 1 ψ = 0.1

Template

202.46930 47.19290 F13277+4727 0.1 0.001544 10.05 9.49 9.60 10.35 Sbc 0.0 10.75 7.54 M51 185.72728 15.82777 F12203+1605 0.4 0.005240 10.53 10.19 9.98 11.22 Sbc 0.0 11.62 8.15 M100 148.97540 69.68221 F09517+6954 0.2 0.000677 9.19 10.41 9.95 E 0.0 10.54 7.18 M82 233.74080 23.49795 F15327+2340 0.4 0.01813 12.15 10.58 E 0.0 11.17 8.15 Arp220

16-band, z < 0.01

175.24310 11.47154 F11383+1144 0.1 0.003312 9.70 9.69 9.24 10.00 Sab 0.0 10.57 7.58 NGC 3810 143.03957 21.50516 F09293+2143 0.2 0.001855 9.70 9.49 9.38 10.41 Scd 0.2 10.79 7.43 NGC 2903 213.89354 36.22261 F14134+3627 0.3 0.009591 10.19 9.60 10.70 Sab 0.65 11.27 8.44 NGC 5529 181.50023 47.47356 F12034+4745 0.3 0.001888 8.90 9.09 8.60 9.65 Sab 0.6 10.22 6.95 NGC 4096 206.59677 43.86664 F13443+4407 0.5 0.008036 9.90 9.99 10.60 Scd 0.4 11.04 7.86 NGC 5297 184.95674 29.61180 F12173+2953 0.7 0.003102 9.64 10.40 Scd 0.0 10.94 7.45 NGC 4274 218.18851 49.45234 F14310+4940 0.4 0.007052 10.60 10.70 Sab 0.4 11.27 7.71 NGC 5676 178.20813 44.12143 F11502+4423 0.5 0.002699 9.59 9.10 9.90 Scd 0.5 10.34 7.40 NGC 3938

Cold log (S 857/S 545) < 0.4

159.78535 41.69160 F10361+4155 2.0 0.002228 8.52 8.10 7.50 sb 0.2 7.52 7.33 179.31494 49.28748 F11547+4933 0.4 0.002592 8.79 8.70 sb 0.0 8.72 6.60 218.19263 9.88910 F14302+1006 0.6 0.004574 9.40 8.92 9.60 Scd 0.2 10.04 7.76 208.22507 –1.12087 F13503-0052 0.4 0.004623 9.64 9.70 Scd 0.5 10.14 7.45 148.79717 9.27136 F09521+0930 0.0 0.004854 8.92 9.40 9.60 Scd 0.0 10.04 7.73 219.79150 5.25526 F14366+0534 0.4 0.005020 9.09 8.62 8.70 10.35 Scd 0.2 10.79 7.54 158.12950 65.03790 F10290+6517 0.4 0.005624 9.40 8.62 9.80 Scd 0.2 10.24 7.48 210.53130 55.79348 F14004+5603 1.4 0.006014 9.05 8.67 10.25 Scd 0.7 10.69 7.50 208.72266 41.30995 F13527+4133 0.0 0.007255 9.51 8.40 9.96 Scd 0.2 10.40 6.76 205.57553 60.77630 F13405+6101 0.3 0.007322 9.20 8.63 9.61 Sbc 0.5 10.01 7.58 228.37207 58.49204 F15122+5841 1.0 0.008474 9.26 8.95 9.51 Scd 0.15 9.95 7.77 231.67357 40.55709 F15248+4044 0.4 0.008743 9.70 9.43 9.41 10.16 Scd 0.7 10.60 8.31 226.95305 54.74415 F15064+5456 0.7 0.01043 10.00 10.16 Scd 0.4 10.60 7.81 126.57545 22.88144 F08233+2303 1.3 0.01794 10.20 10.13 9.81 Scd 0.3 10.25 8.99 231.43570 52.44624 F15243+5237 0.3 0.01948 10.19 9.81 10.44 Sab 0.2 11.01 8.64 237.68201 55.60954 F15495+5545 0.2 0.03974 10.55 10.52 10.20 10.70 Sab 0.0 11.27 9.34 66.76954 –49.12881 F04257-4913 0.8 0.05828 10.62 11.55 10.85 Sab 0.0 11.42 9.43

Notes. Table columns are: ERCSC RA and Dec, IRAS FSC name, separation between ERCSC and IIFSCz position, spectroscopic redshift, luminosity in cirrus φ = 5, φ = 1andφ = 0.1 components, luminosity in M 82 and Arp220 starburst components, optical luminosity, optical SED type, extinction (additional to that inherent to the individual templates), stellar mass and dust mass. Total far-IR luminosity can be obtained by summing the various different components. Stellar mass and dust mass are calculated as in Rowan-Robinson et al. (2008), where the methods and uncertainties in the derived quantities are discussed in detail. Where the sources have a well known name this is given beneath the IRAS name. All luminosities are measured in solar luminosities.

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Fig. 11. Template fits for 8 nearby galaxies with detections in 16 bands. Blue curve is cirrus template used for solar neighbourhood (Tdust = 15–20 K, φ = 1), other components shown as dotted lines.

Fig. 12. 545 GHz flux density versus redshift, showing loci for Arp220 Fig. 13. S 857/ S 545 colour-ratio versus redshift. Points in red are IRAS 12 13 template with LIR = 10 and 10 L . Red dots are those galaxies in the BGS sources, points in blue are those sources identified as having T2 < IRAS Bright Galaxy Survey (BGS). We show here that the BGS does 10 K on the basis of parametric fits. not sample as wide a range of galaxy properties as the Planck-IIFSCz sample discussed here.

A16, page 12 of 16 Planck Collaboration: Planck early results. XVI.

Fig. 14. Template fits for cool ERCSC galaxies (log10(S 857/S 545) < 0.4). Blue curve: cirrus with φ = 1, green curve: cirrus with φ = 0.1. previously only been hinted at, largely in dwarf galaxies. The that previous studies of dust in local galaxies have been biased temperature of this dust, is similar to that found in the solar away from such luminous cool objects. We also find that the dust neighbourhood. We also find that some local galaxies are both SEDs in most galaxies are better described by parametric mod- luminous and cool, with properties similar to those of the dis- els containing two dust components, one warm and one cold, tant SMGs uncovered in deep submm surveys. This suggests with the cold component reaching temperatures as low as 10 K.

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Some objects have SEDs dominated by this cold material. These Frayer, D. T., Fadda, D., Yan, L., et al. 2006, AJ, 131, 250 conclusions are based on both parametric fits and by detailed fit- Galametz, M., Madden, S., Galliano, F., et al. 2009, A&A, 508, 645 ting of radiative transfer derived physical templates to the SEDs. Galliano, F., Madden, S. C., Jones, A. P., Wilson, C. D., & Bernard, J. 2005, A&A, 434, 867 Other physical or parametric descriptions of dust, for example Gispert, R., Lagache, G., & Puget, J. L. 2000, A&A, 360, 1 where β varies with wavelength, might lead to different results Hughes, D. H., Serjeant, S., Dunlop, J., et al. 1998, Nature, 394, 241 regarding this very cold component. We note in this context, Jaffe, A. 1996, ApJ, 471, 24 however, that SED fits for galaxies in the H-ATLAS survey are Jaynes, E. 2003, Probability Theory: the Logic of Science (Cambridge University Press) reaching similar conclusions to this study (Smith et al., in prep.). Kovács, A., Chapman, S. C., Dowell, C. D., et al. 2006, ApJ, 650, 592 This paper represents the first exploitation of Planck data for the Lamarre, J., Puget, J., Ade, P. A. R., et al. 2010, A&A, 520, A9 study of a large sample of galaxies in the local Universe. As such Leahy, J. P., Bersanelli, M., D’Arcangelo, O., et al. 2010, A&A, 520, A8 it indicates both the benefits and hazards of the ERCSC for this Lewis, A., & Bridle, S. 2002, Phys. Rev. D, 66, 103511 work, but it also clearly demonstrates the tremendous potential Mandolesi, N., Bersanelli, M., Butler, R. C., et al. 2010, A&A, 520, A3 Mennella, A., Bersanelli, M., Butler, R. C., et al. 2011, A&A, 536, A3 of Planck data for the study of dust in galaxies. Odenwald, S., Newmark, J., & Smoot, G. 1996 [arXiv:astro-ph/9610238] Oliver, S. J., Wang, L., Smith, A. J., et al. 2010, A&A, 518, L21 Planck Collaboration 2011a, A&A, 536, A1 Planck Collaboration 2011b, A&A, 536, A2 Acknowledgements. This research has made use of the NASA/IPAC Planck Collaboration 2011c, A&A, 536, A7 Extragalactic Database (NED) which is operated by the Jet Propulsion Planck Collaboration 2011d, A&A, 536, A8 Laboratory, California Institute of Technology, under contract with the National Planck Collaboration 2011e, A&A, 536, A9 Aeronautics and Space Administration. Use was also made of data from Planck Collaboration 2011f, A&A, 536, A10 the (SDSS) and the Two Micron All Sky Survey Planck Collaboration 2011g, A&A, 536, A11 (2MASS). Funding for the SDSS and SDSS-II has been provided by the Planck Collaboration 2011h, A&A, 536, A12 Alfred P. Sloan Foundation, the Participating Institutions, the National Science Planck Collaboration 2011i, A&A, 536, A13 Foundation, the U.S. Department of Energy, the National Aeronautics and Planck Collaboration 2011j, A&A, 536, A14 Space Administration, the Japanese Monbukagakusho, the Max Planck Society, Planck Collaboration 2011k, A&A, 536, A15 and the Higher Education Funding Council for England. The SDSS Web Site Planck Collaboration 2011l, A&A, 536, A16 is http://www.sdss.org/. 2MASS is a joint project of the University of Planck Collaboration 2011m, A&A, 536, A17 Massachusetts and the Infrared Processing and Analysis Center/California Planck Collaboration 2011n, A&A, 536, A18 Institute of Technology, funded by the National Aeronautics and Space Planck Collaboration 2011o, A&A, 536, A19 Administration and the National Science Foundation. The Planck Collaboration Planck Collaboration 2011p, A&A, 536, A20 acknowledges the support of: ESA; CNES and CNRS/INSU-IN2P3-INP Planck Collaboration 2011q, A&A, 536, A21 (France); ASI, CNR, and INAF (Italy); NASA and DoE (USA); STFC and Planck Collaboration 2011r, A&A, 536, A22 UKSA (UK); CSIC, MICINN and JA (Spain); Tekes, AoF and CSC (Finland); Planck Collaboration 2011s, A&A, 536, A23 DLR and MPG (Germany); CSA (Canada); DTU Space (Denmark); SER/SSO Planck Collaboration 2011t, A&A, 536, A24 (Switzerland); RCN (Norway); SFI (Ireland); FCT/MCTES (Portugal); Planck Collaboration 2011u, A&A, 536, A25 and DEISA (EU). A description of the Planck Collaboration and a list of Planck Collaboration 2011v, The Explanatory Supplement to the Planck Early its members, indicating which technical or scientific activities they have Release Compact Source Catalogue (ESA) been involved in, can be found at http://www.rssd.esa.int/index.php? 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3 Astroparticule et Cosmologie, CNRS (UMR7164), Université Denis 36 INAF – Osservatorio Astronomico di Padova, Vicolo Diderot Paris 7, Bâtiment Condorcet, 10 rue A. Domon et Léonie dell’Osservatorio 5, Padova, Italy Duquet, Paris, France 37 INAF – Osservatorio Astronomico di Roma, via di Frascati 33, 4 Astrophysics Group, Cavendish Laboratory, University of Monte Porzio Catone, Italy Cambridge, J J Thomson Avenue, Cambridge CB3 0HE, UK 38 INAF – Osservatorio Astronomico di Trieste, via G.B. Tiepolo 11, 5 Atacama Large Millimeter/submillimeter Array, ALMA Santiago Trieste, Italy Central Offices, Alonso de Cordova 3107, Vitacura, Casilla 39 INAF/IASF Bologna, via Gobetti 101, Bologna, Italy 763 0355, Santiago, Chile 40 INAF/IASF Milano, via E. Bassini 15, Milano, Italy 6 CITA, University of Toronto, 60 St. George St., Toronto, 41 INRIA, Laboratoire de Recherche en Informatique, Université ON M5S 3H8, Canada Paris-Sud 11, Bâtiment 490, 91405 Orsay Cedex, France 7 CNRS, IRAP, 9 Av. Colonel Roche, BP 44346, 31028 Toulouse 42 IPAG: Institut de Planétologie et d’Astrophysique de Grenoble, Cedex 4, France Université Joseph Fourier, Grenoble 1/CNRS-INSU, UMR 5274, 8 California Institute of Technology, Pasadena, California, USA 38041 Grenoble, France 9 DAMTP, University of Cambridge, Centre for Mathematical 43 ISDC Data Centre for Astrophysics, University of Geneva, ch. Sciences, Wilberforce Road, Cambridge CB3 0WA, UK d’Ecogia 16, Versoix, Switzerland 10 DSM/Irfu/SPP, CEA-Saclay, 91191 Gif-sur-Yvette Cedex, France 44 Imperial College London, Astrophysics group, Blackett Laboratory, 11 DTU Space, National Space Institute, Juliane Mariesvej 30, Prince Consort Road, London, SW7 2AZ, UK Copenhagen, Denmark 45 Infrared Processing and Analysis Center, California Institute of 12 Departamento de Física, Universidad de Oviedo, Avda. Calvo Sotelo Technology, Pasadena, CA 91125, USA s/n, Oviedo, Spain 46 Institut Néel, CNRS, Université Joseph Fourier Grenoble I, 25 rue 13 Department of Astronomy and Astrophysics, University of Toronto, des Martyrs, Grenoble, France 50 Saint George Street, Toronto, Ontario, Canada 47 Institut d’Astrophysique Spatiale, CNRS (UMR 8617) Université 14 Department of Physics & Astronomy, University of British Paris-Sud 11, Bâtiment 121, Orsay, France Columbia, 6224 Agricultural Road, Vancouver, British Columbia, 48 Institut d’Astrophysique de Paris, CNRS UMR 7095, Université Canada Pierre & Marie Curie, 98bis boulevard Arago, Paris, France 15 Department of Physics, Gustaf Hällströmin katu 2a, University of 49 Institute of Astronomy and Astrophysics, Academia Sinica, Taipei, Helsinki, Helsinki, Finland Taiwan 16 Department of Physics, Princeton University, Princeton, New Jersey, 50 Institute of Astronomy, University of Cambridge, Madingley Road, USA Cambridge CB3 0HA, UK 17 Department of Physics, Purdue University, 525 Northwestern 51 Institute of Theoretical Astrophysics, University of Oslo, Blindern, Avenue, West Lafayette, Indiana, USA Oslo, Norway 18 Department of Physics, University of California, Berkeley, 52 Instituto de Astrofísica de Canarias, C/Vía Láctea s/n, La Laguna, California, USA Tenerife, Spain 19 Department of Physics, University of California, One Shields 53 Instituto de Física de Cantabria (CSIC-Universidad de Cantabria), Avenue, Davis, California, USA Avda. de los Castros s/n, Santander, Spain 20 Department of Physics, University of California, Santa Barbara, 54 Jet Propulsion Laboratory, California Institute of Technology, 4800 California, USA Oak Grove Drive, Pasadena, California, USA 21 Department of Physics, University of Illinois at Urbana-Champaign, 55 Jodrell Bank Centre for Astrophysics, Alan Turing Building, School 1110 West Green Street, Urbana, Illinois, USA of Physics and Astronomy, The University of Manchester, Oxford 22 Dipartimento di Fisica G. Galilei, Università degli Studi di Padova, Road, Manchester, M13 9PL, UK via Marzolo 8, 35131 Padova, Italy 56 Kavli Institute for Cosmology Cambridge, Madingley Road, 23 Dipartimento di Fisica, Università La Sapienza, P. le A. Moro 2, Cambridge, CB3 0HA, UK Roma, Italy 57 LERMA, CNRS, Observatoire de Paris, 61 avenue de 24 Dipartimento di Fisica, Università degli Studi di Milano, via Celoria, l’Observatoire, Paris, France 16, Milano, Italy 58 Laboratoire AIM, IRFU/Service d’Astrophysique – CEA/DSM – 25 Dipartimento di Fisica, Università degli Studi di Trieste, via A. 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